Circular scale electrical musical instrument



Aug. 12, 1958 L. HAMMOND CIRCULAR SCALE ELECTRICAL MUSICAL INSTRUMENT 2Sheets-Sheet 1 Filed June 23, 1950 VALUES OF RESISTORS cowfiecrme IKEY-OPERATED SWITCHES TO GENERATORS 7 KEY (OHMS) c. c! o E. F F*6 6 A 5c.

LOW MIDDLE HIGH OCTAVE OCTAVE OCTAVE GENERATOR GENERATOR GENERATOR 6/-oo as g-fi Aug.'l2, 1958 HAMMOND 2,345,913

CIRCULAR SCALE ELECTRICAL MUSICAL INSTRUMENT Filed June 23, 1950 2Sheets-Sheet 2 iii United States Patent CIRCULAR SCALE ELECTRICALMUSICAL INSTRUMENT Laurens Hammond, Chicago, Ill., assignor to HammondOrgan Company, a corporation of Delaware Application June 23, 1950,Serial No, 169,901

6 Claims. (Cl. 84-1.01)

My invention relates generally to electrical musical instruments andmore particularly to a method and apparatus for producing a novel effectin the perception of the pitch of musical tones.

It is generally stated that the apparent pitch of a com plex musicaltone is determined by the pitch of the lowest frequency component of thetone. It is known that this is not strictly true. One known exception isthat a complex musical tone having at least second and third harmoniccomponents but no fundamental component is perceived by the listener ashaving the pitch of the absent fundamental.

I have discovered that a novel and very startling musical effect may beproduced, for example, with a musical instrument adapted to providemusical tones that change in quality in a certain manner as the toneschange in pitch. If the keys of an octave of such an instrument aredepressed one after the other in a deliberate manner as in playing thechromatic musical scale, from low pitch to high pitch, each successivetone apparently has the pitch corresponding to the depressed key, andthe series of tones apparently is that of the ascending chromatic scale.However, if after the twelfth tone of the octave has been played, thefirst is again sounded, the surprising fact is that the tone producedthen seems to a listener to be of higher pitch than the twelfth tone.

The player thus may play an ascending scale in the same octaverepeatedly and it is perceived by the listeners as a progression oftones of uninterruptedly ascending pitch. This illusion is verypowerful, so much so that a listener hearing it for the first time isutterly perplexed and cannot believe his ears.

With an instrument embodying a variant of the invention, a person mayplay the ascending chromatic scale through two octaves of keys and findby comparing the last tone with the first that there is only one octaveof pitch diiference between the two although, as the scale was played,each successive tone was apparently a semitone higher than the precedingtone.

The effects of playing a descending scale, as might be expected, aresimilar, in reverse, to the effects produced by playing an ascendingscale. Each tone is apparently of lower pitch than the preceding one,but the thirteenth tone of the descending scale seems to be of lowerpitch than the first tone sounded.

Broadly speaking these results are obtained by changing the quality ofthe tone slightly with each semitone for some or all of the semitoneintervals of an octave, by progressively increasing the intensity of alow frequency tone component while at the same time progressivelydecreasing the intensity of a high frequency tone component as the pitchincreases. The two tone components may difier in pitch by one or moreoctaves.

Thus an object of this invention is to produce a novel, unexpectedmusical effect.

A further object is to provide apparatus for combining tone componentsto provide a series of tones for producing a novel scale efiect wherebythe tones sounded.

ICC

in succession are perceived as a scale although the first and last notesof an octave have the same pitch.

A further object is to provide apparatus for producing a circular scalemusical effect.

A further object is to provide apparatus for producing scale tonescharacterized in that the actual change in pitch over a given range isless than the apparen change- A further object is to provide apparatusfor producing accompaniment musical tones.

A further object is to provide apparatus for producing accompanimenttones for a multi-octave musical instrument having playing keys, thenumber of different tones being less than the number of keys.

Other objects and advantages of this invention will appear from thefollowing description together withthe drawings which disclose thedetails of illustrative cmbodiments of this invention in order thatthose skilled in the art may readily understand and practice its basicprinciples. ,A complete and concise statement of the patentable scope ofthis invention is set forth in the appended claims.

In the drawings, Figure 1 is a diagrammatic representation of anillustrative embodiment of this invention;

Figure 2 is a tabulation of illustrative resistance values of theresistors of Fig. 1;

Figures 3, 4 and 5 are diagrams illustrating the pri ciples of thisinvention;

Figure 6 is a diagrammatic representation .of a modified form of thisinvention;

Figures 7 and 8 illustrate tone wheel generators which may be employedas parts of the apparatus illustrated in Fig. 6;

Figure 9 illustrates a magnetic record reproducing mechanism which mayform a part of the apparatus illustrated in Fig. 6.; and

Figure 10 is a diagram illustrating the principles of this invention.

By circular scale as used in this application, is meant a progressivechange in tone quality throughout the range of one or two octaveswhereby the lowest tone within the range are complex tones comprising arelatively low strength unison tone and a relatively high strengthoctave tone While the highest pitched tone within the range consists ofa relatively high strength complex unison tone and a relatively lowstrength .octavely related complex tone, the intermediate tones withinthe range of an octave or two octaves being graded progress sivelybetween the lowest and highest tones.

Fig. 1 illustrates a musical instrument having thirteen keys 10, thefour typical keys 10 illustrated bein the three lowest and the highestpitched keys .10, designated as C3, C3#, D3 and C4.

Each key 10 has an operating connection with an individual middle octaveswitch 14, with arhigh octave switch 16, and, except for .the C3 and C4keys 1 0, with a low octave switch 18.

A rank of twelve middle octave generators or sources 20 are provided,three representatives ,of which are illustrated, for producing scaletone signals differing by semitone pitch intervals and extending .over amusical octave beginning, for example, with the .note C3, 261.6 cyclesper second (C. P. 8.), and progressing npward through C3# (277.2 C. P.8.), D3 (293.7 C. P. 8.), ,and so forth.

Three high octave generators ,22 are illustrated as representative of arank of twelve such generators 22 provided for producing tone signalsone octave h gher in pitch than the signals produced by thecorrespondingly designated middle octave generators 2.0. Thus thegenerators 22 respectively designated C4, C4# and D4 :provide signals at523.3 C. P. 8., 554.4 C. P. S., and 5873 C. P. S.

A rank of eleven low octave generators 24 are provided, two typicalgenerators 24 being illustrated, for producing tone signals one octavelower in pitch than the signals from the corresponding middle octavegenerators 20. Thus the generators 24 respectively designated C24? andD2 produce signals at 138.6 C. P. S. and 146.8 C. P. S. No generator 24of the pitch C2 is provided.

One output terminal of each of the generators 20, 22, 24 is grounded.One terminal of each of the switches 14, 16, 18 is connected with oneend of a low impedance primary winding 26 of a transformer 28, the otherend of'the winding 26 being grounded. The secondary winding 30 of thetransformer 28 is connected with the input of an amplifier or outputsystem 32. One end of the secondary 30 is grounded. The output of theamplifier 32 is connected with a speaker or translator 34.

The other terminal of each middle octave switch 14 is connected throughan individual resistor R36 with the ungrounded terminal of the middleoctave generator 20 having the same pitch designation. Thus, the C noteswitch 14 is connected with the generator 20 designated C3, the C# noteswitch 14 with the C3# generator 20, the D switch 14 with the D3generator 20, and so forth. The switches 14 and resistors R36 may beregarded as parts of the respective generators 20.

In like manner, each of the high octave switches 16 is connected by anindividual resistor R38 with the high octave generator 22 having thesame pitch designation. Thus the C switch 16 is connected with the C4generator 22, the C# switch 16, with the C4# generator 22,- and soforth.

Each of the low octave switches 18 is connected through an individualresistor R40 with the corresponding low octave generator 24, the C#switch 18 being connected with the C2# generator 18, and so on.

The resistors R36, R38, R40 regulate the amplitudes of the outputsignals from the generators 20, 22, 24. The values of R36, R38 and R40should be large compared with the impedance of the transformer primary26 and with the internal impedances of the generators 20, 22, 24. Asindicated in Fig. 2, all the middle octave resistors R36 may have thesame value, such as 39 ohms. The values of the high octave resistors R38are graded, roughly in a geometric series, between a value such as 39ohms for the C notes and 330 ohms for the B notes. The low octaveresistors R40 are graded geometrically between values such as 330 ohmsfor the C# notes and 47 ohms for the B notes.

Illustrative values of R36, R38 and R40 are given in order that thoseskilled in the art may more readily grasp the fundamental principles ofthis invention. It will be understood that many other appropriate valuesmay be employed.

If the C3 key is depressed, the associated switches 14 and 16 are closedand the C3 and C4 generators 20 and 22 are connected through R36 and R38respectively to the primary 26 of the transformer 28 and thence to theoutput system 32. Thus the tones C3 at 261.6 C. P. S. and C4 at 523.3 C.P. S. are sounded simultaneously. Since, as shown in Fig. 2, R36 and R38have the same values for this key 10, the tones have equal intensities,and an octave coupler effect is produced. The apparent pitch is that ofthe lower frequency C3 component.

If the C3 key 10 is released and the C3# key 10 depressed, thegenerators 20 (C3#), 22 (C4#) and 24 (C2#) are connected with the outputsystem 32 through R36, R38 and R40 respectively and the three generatorsare concurrently sounded to produce a tone comprising three octavelyrelated components. As seen in Fig. 2, the middle octave (C3#) componenthas the same amplitude as before since the values of all of theresistors R36 are the same, but the high octave component (C4#) has aslightly smaller amplitude than before because the value of R38 is about20 percent greater. The amplitude of the low octave component (C2#) isvery small be- 4 l cause of the relatively high value of R40. In fact,the amplitude of the low octave component is so small that the apparentpitch of the composite tone is that of the middle octave (C3#) componentand the apparent pitch thus is higher than that of the preceding tone.

If the C3# key 10 is released and the D3 key 10 depressed, a tonecomprising middle octave (D3), high octave (D4) and low octave (D2)components is sounded. It may be seen in Fig. 2 that the intensity ofthe low octave, component is slightly greater than before because of thesmaller value of R40, and the intensity of the high octave component isdecreased slightly because of the greater value of R38 while theintensity of the middle octave component remains the same as before.Since all three of the components have increased in pitch from theprevious tone the apparent over-all pitch of the tone is increased also.

As the remaining keys 10 of the scale are successively depressed, inascending order, the proportionate intensity of the low octave componentprogressively increases while the intensity of the high octave componentprogressively decreases. These progressive changes in intensity areclearly illustrated by the diagram of Fig. 3 in which the lowest arrows50, drawn with light lines, represent the intensities of the lowfrequency component, the middle arrows 52, drawn with medium weightlines, represent the intensities of the middle octave component and theupper arrows 54, drawn with heavy lines, represent the intensities ofthe high octave component. As shown in Fig. 3, when the note B3 isreached the intensity of the low octave component is nearly as great asthe intensity of the middle octave component while the intensity of thehigh octave component is reduced to a very small value. .The apparentpitch of this tone is that of the low octave component and is actually asemitone lower than the apparent pitch of the C3 tone which was firstsounded. If the C4 key 10 is depressed the tone sounded is the same asthat produced by the depression of the C3 key .10 but the tone seems tobe higher in pitch than the preceding tone in the scale. With aninstrument such as this the pitch of the tones seems to change in thenormal manner from note to note as a scale is played, but the pitch ofthe last scale tone is the same as that of the first. Such a scale mayaptly be termed a circular scale."

In Fig. l the components connected to the output by operation of a givenkey 10, taken together, may be regarded as a single source of a complexoctave coupler type signal. For example, one such complex sourcecomprises the components connected with the D3 key 10, including the D3generator 20 and the associated resistor R36 and switch 14 whichcontribute the middle octave or fundamental signal component, the D2generator 24 and the associated resistor R40 and switch 18 whichcontribute the low octave or suboctave coupler component, and the D4generator and the associated resistor R38 and switch 16 which furnishthe high octave or octave coupler component. The middle arrows 52 in thediagram of Fig. 3 may be regarded as indicating the percentage magnitudeof the fundamental component, the lower arrows 50 the percentagemagnitude of suboctave coupler, and the upper arrows 54 the percentagemagnitude of the octave coupler. The fundamental com-- ponent has thesame percentage amplitude for all the tones of the scale but thesuboctave coupler effect increases progressively from tone to tone inascending order and the octave coupler effect decreases progressivelyfrom tone to tone.

The principles of this invention may be applied in many difierent waysto provide a considerable variety of apparatus capable of producingdifllerent but basically similar musical results. Fig. 4 illustrates onesuch variation. A polar diagram is shown in which the arrows 60originating at the origin or center of the diagram represent theintensities of a low octave or suboctave tone component and the outerarrows 62 terminating at a circular envelope line 63 represent theintensities of a high octave or fundamental tone component. The twocomponents may differ in pitch by a single octave. The diagramillustrates how the components may be combined to produce a circularscale effect. The tone A comprises the fundamental component only. Asmall amount of the suboctave component is introduced into the tone Alito produce a suboctave coupler effect and the fundamental component isreduced slightly so that the total amplitude remains constant. Themagnitude of the suboctave coupler effect increases progressivelythrough the tones B, C, Cit, D, Dtt, E,, F, Fit, G and Git while themagnitude of thev fundamental component progressively decreases, asindicated by the diagram. For tones such as Fit, G and Git the intensityof the suboctave coupler component. is considerably greater than that ofthe fundamental component, and the suboctave component tends to dominatethe tone and to determine the apparent or subjective pitch. The tone Githas a lower subjective pitch then the tone A because the suboctavecomponent which dominates the tone G4 is one semitone lower in pitchthan the fundamental component which dominates the tone A.

With the aid of the disclosure herein, those skilled in the art willreadily be able to devise an apparatus for producing a scale of toneshaving the qualities illustrated in Fig. 4. For example the apparatus ofFig. 1 may readily be modified to provide such a scale of tones byomitting the generators 24, the resistors R40 and the switches 13 and bychanging the values of the resistors R36 and R38. The generators 22 maybe utilized tov furnish. the fundamental components and the generators20, to furnish the suboctave coupler components. A generator is notrequired to produce the tone A since a generator 22 produces thefundamental component which comprises the entire tone.

The diagram of Fig. 4 has been drawn in polar form inv order toillustrate the aptness of the name circular scale and to show that thechange in tone quality from tone to:tone is so gradual that the tonesmay be sounded in. succession without unusual discontinuities in pitch.If the tones are sounded in ascending order beginning with any of thetones, they are perceived as a regularly ascending scale although thereis no net change in pitch over a complete octave of tones.

Fig. 5 shows another illustrative. application of the fundamentalprinciples of this invention. of. the diagram is similar to that of Fig.3, the lower arrows 70, drawn with light lines, representing theamplitudes of a suboctave tone component and the upper arrows 72, drawnwith heavy lines, representing the amplitudes of afundamental tonecomponent. As shown, the circularization of the scale is accomplishedthrough a range of only four tones rather than acomplete octave. Thetones C, Cit, D, Dtt and E consist entirely of the fundamentalcomponent. If they are successively sounded the first five tones of anorthodox chromatic scale are heard. The tones F, Fit, G and Git compriseboth the fundamental and. suboctave components, the suboctave componentfurnishing about 10 percent of. the intensity of the tone F, 25 percentof the intensity of the tone Fit, 56 percent ofv the intensity of thetone G and 75 percent of the intensity of the tone Git. The. remainingtones A, At. and B consist entirely of the suboctave component. If thetwelve tones are sounded in succession there is a slight change ofquality between the tones Ev and F, but the change isso small that it ishardly perceptible and the pitch seems to rise a normal. semitonebetween the two tones. Likewise there is a change. in quality betweenthe F and Fit tones, but the change from 10 percent to' 25 percentsuboctave coupler eifect is so slight as to be hardly perceptible andthe illusion of increasing pitch ispreserved. The same is true of thechanges in quality between the tone Fit and G, G and Git, and Git and A.Although the. actual pitch of the tone A is lower than The scheme thatof the tone E, a powerful illusion of increasing pitch is produced ifthe tones B through A arev successively sounded because the change fromthe fundamental range to the suboctave range is accomplished sogradually.

Fig. 6 illustrates how the circular scale principle may be applied toprovide accompaniment tones for a multioctave keyboard type electricalmusical instrument. It will be apparent to those skilled in the art thata circular scale instrument is not well adapted to play solo melodyparts in which large intervals of pitch change are encountered becausethe circular scale illusion depends upon the successive sounding ofadjacent tones as in playing a chromatic or diatonic scale. However, acircular scale instrument may be employed as an accompaniment section ofan instrument which also comprises a solo. section. Both the solosectionand the accompaniment section may be operated by a single keyboard, orseparate keyboards may be employed. Only the accompanh ment section ofsuch an instrument is shown in Fig. 6 and the solo section may he of anydesired construction.

The seven playing keys illustrated in Fig. 6 represent the keys of afour octave instrument. Each of the keys 80 has an operating connectionwith a switch 82. One terminal of each of the switches 82 is connectedby means of a collector bus-bar 84 to an input terminal 86 of anamplifier or output system 88 having a low-impedance input, and theother input terminal 90 of the amplifier is grounded. The output of theamplifier 88 is connected to a speaker or other output device 92. Twelvegenerating systems or sources 94 are provided to pro-- duce tonescorresponding with the twelve musical notes of an octave. Threerepresentative. generators 94 designated C, C# and B are illustrated.

One output terminal 93 of each generator is grounded. Each of theswitches 82 is connected through an individual resistor R to theungrounded terminal 95 of one of the generators 94, all of the Cswitches 82 being connected to the C generator 94, all of the C#switches 82 to the C# generator 94, and so forth. By this connection aplurality of octaves of keys may be served by a single octave ofgenerators.

The generators 94 are designed to provide tones having different tonequalities so that the circular scale effect is produced when the keys 80are successively depressed. For example, each generator 94 may comprisea plurality of oscillators, somewhat as illustrated in Fig. I, adjustedto produce high, low and middle octave components in the proportionssuggested in Fig. 3, the amplitude of the low octave componentincreasing and the amplitude of the high octave component decreasing asan ascending scale is played. Alternately, each generator 94 maycomprise oscillators to produce fundamental and suboctave components inthe proportions indicated either in Fig. 4 or in Fig. 5.

Figs. 7 and 8 illustrate another modified construction of the generators94. According to this modification the generators are of the type shownin the patent to Laurens Hammond, No. 1,956,350 entitled ElectricalMusical Instrument, including magnetically permeable tone or phonicwheels which rotate adjacent permanent magnets 109 having pickup coils111. Figs. 7 and 8 illustrate such tone wheels which are adapted toproduce circular scale tones.

Each of the generators 94 may include a tone wheel 112 suchas thatillustrated in Fig. 8. Sixteen notches or undulations 114, 116 and 118are equally spaced around the periphery of the tone wheel 112. Thenotches 114, having azimuths of 0, 90, 180 and 270, are of vari abledepth; the four notches 116, having azimuths of 45, 225 and 315, are ofan intermediate or medium depth such as inch and the remaining notchesare of small depth such as inch. In the tone wheel 112 forming a part ofthe C generator 94 the notches 114 have the same depth as the notches116. This. particular tone wheel is illustrated in Fig. 7. In the tonewheel 112 forming a part of the B generator 94 the notches 114 have adepth such as %2 inch which is considerably greater than the depth ofthe notches 116. The notches 114 in the tone wheel 112 for intermediatenote generators 94 are graded in depth between these extremes, thenotches 114 becoming progressively deeper for the higher pitched notes.Thus the notches 114 in the C# phonic wheel 112 are slightly deeper thanthose inthe C tone wheel 112, the notches 114 in the D tone wheel 112are slightly deeper than those in the C# tone wheel 112, and so forth.

The phonic wheels 112 are rotated at different speeds to producedifferently pitched signals. The speed of the phonic wheel 112 forming apart of the C generator 94 is the lowest and the speed of the phonicwheel forming a part of the B generator 94 is the highest.

When the notches 114 are the same depth as the notches 116, asillustrated in Fig. 7, the tone wheel generator 94 produces a tonesignal having fundamental and octave components, the fundamentalcomponent being due primarily to the deeper notches 114 and 116 and theoctave component being due primarily to the shallower notches 118. Whenthe notches 114 are deeper than the notches 116 the tone wheel generatorproduces a tone signal having a suboctave component (with its harmonics)in addition to the fundamental and octave components (with theirrespective harmonics). The suboctave component becomes greater andgreater relative to the fundamental and octave components when thenotches 114 are made deeper and deeper than the notches 116. Thus thetone produced upon depression of the C1 key 80 has fundamental andoctave components of approximately equal intensities. The tone producedby the depression of the C1# key 80, has a small suboctave component,but the suboctave coupler effect is so slight that the C1# tone is heardas having a higher pitch than the C1 tone. As an ascending scale isplayed the suboctave component gradually dominates the tones so that theB1 tone is heard as having the pitch of the suboctave component. The C2tone, which has the same pitch and quality as the C1 tone, then has ahigher apparent pitch than the B1 tone. The same circular scale isrepeated if the succeeding octaves of keys 80 are successivelydepressed.

The provision of an accompaniment section employing the circular scaleprinciple effects a substantial reduction in the number of accompanimentgenerators required for a multioctave instrument. Accompaniment chordsand simple counter-melodies may be played with the circular scaleaccompaniment section with pleasing musical results. In addition, thecircular scale effect may be utilized to produce novel melodic andaccompaniment effects which are impossible with a conventional musicalinstrument.

The simultaneous depression of more than one octavely related key 80produces additive effects because of the provision of an individualdecoupling resistor R100 for each key switch 82. Thus, if the C1 key 80is depressed, closing the Cl switch 82, a tone signal from the Cgenerator 94 is transmitted through the C1 resistor R100 to the outputsystem 88. Simultaneous depression of the C2 key 80, closing the C2switch 82, provides an additional path through the C2 resistor R100 fromthe C generator 94 to the output system, and the C tone is sounded withadditional intensity.

Fig. 9 illustrates another modified form of the generators 94 of Fig. 6.According to this modification each generator may comprise a record 120,which is illustrated as a magnetic wire, together with apparatus adaptedto reproduce the signals recorded upon the record 120. Such apparatusmay include a supply spool 122, a take-up spool 124 and a pick-up ortransducing element 126 having output terminals 93 and 95 correspondingwith the similarly designated output terminals of the generators 94 inFig. 6. Any ofv the many well-known types of records and re- 'mentsdescribed herein.

producing apparatus may be employed. Each of the records may beimpressed with a tone signal having octavely related componentsproportioned according to the principles of this invention. High, lowand middle octave tone components may be combined according to thearrangement illustrated in Fig. 3 or, if desired, fundamental andsuboctave components may be combined according to either of thearrangements illustrated in Figs. 4 or 5, for example.

The tone signal components for recording upon the record 120 may bederived from any desired sources.

Fig. 10 illustrates a further application of the principles of thisinvention in which the pitch changes one octave over a two octave rangeof notes. In the diagram, the lower arrows 130, drawn with light weightlines, represent the amplitudes of a suboctave component, the middlearrows 132, drawn with medium weight lines, represent the intensities ofa fundamental tone component and the upper arrows 134, drawn with heavylines, represent the intensities of an octave tone component. The lowesttone C comprises fundamental and octave components having approximatelyequal amplitudes. introduced into the next tone C# and the amplitude ofthe octave component is correspondingly reduced so that the totalamplitude remains unchanged. The amplitude of the suboctave componentbecomes greater and the amplitude of the octave componentcorrespondinglysmaller with each successive tone taken in ascendingorder through two octaves until with the twenty-fifth one octavedifference in apparent pitch between the high-' est and the lowest Ctones although the scale seems to" ascend through a full two octaves oftones because of the very gradual introduction of the suboctavecomponent; No unusual discontinuities in pitch or tone quality are heardas a scale is played.

It will be apparent to those skilled in the art that the I principles ofthis invention may be applied advantageously to produce a startingcircular scale effect. Moreover, by utilizing the principles of thisinvention a muiti-octave musical instrument may be produced having onlya single octave of accompaniment tone sources. This arrangement has theconsiderable advantages of simplicity and economy.

In some of the accompanying claims designation of the keys is by number,merely for clarity of definition of the invention, the numbersthemselves being only of relative significance.

. While I have disclosed this invention by describing and explainingcertain illustrative embodiments, it will be understood by those skilledin the art that the principles of this invention may be applied in manyalternative and equivalent ways to provide structures which may differin their details from those of the illustrative embodi- Therefore, Iwish to include within the scope of the appended claims suchmodifications and variations.

I claim:

1. An electrical musical instrument for playing a circular scale;comprising a plurality of scale tone signal sources including individualphonic wheels having a plurality of equally spaced notches, said notchesbeing alternately deep and shallow, an output system coupled with saidsources, and a plurality of playing keys connected with said sources forsounding said sources individually, said sources including a group ofsources comprising phonic wheels having said deep notches which arealternately very deep and less deep, said very deep notches of thesources of said group in ascending order being progressively deeper anddeeper.

2. In an electrical musical instrument having an output system includingan electroacoustic translating means,

A small amount of the suboctave component is the combination of aplurality of playing keys, a plurality of sources of electrical musicaltone signals of pitches corresponding to successive semitone intervalsof the tempered musical scale, and means operable by the keys to causesubstantially dilferent tone quality signals to be transmitted from thesources to the output system, the quality of the tone signals beingcharacterized by having sub-octave partials of progressively increasingamplitude as an ascending chromatic or diatonic scale is played.

3. The combination set forth in claim 2 in which the quality of the tonesignals is additionally characterized by having unison partials ofprogressively decreasing amplitude as an ascending chromatic or diatonicscale is played.

4. The combination set forth in claim 2 in which the quality of the tonesignals is additionally characterized by having unison partials ofsubstantially constant amplitude, and by having octave partials ofprogressively decreasing amplitude as an ascending chromatic or diatonicscale is played.

5. The combination set forth in claim 4 which includes a series of atleast twenty-five successive semitone 10 6. The combination set forth inclaim 2 which includes a series of at least thirteen successive semitonekeys and in which the quality of the tone signal transmitted to theoutput system upon playing of the thirteenth key is substantially thesame as that transmitted to the output sysem upon playing the first key.

References Cited in the file of this patent UNITED STATES PATENTS1,665,331 Thomson Apr. 10, 1928 1,893,250 Severy Jan. 3, 1933 2,165,707Jacobs July 11, 1939 2,221,814 Reid Nov. 19, 1940 2,227,068 Curtis Dec.31, 1940 2,227,100 Manatt Dec. 31, 1940 2,229,755 Manatt Jan. 28, 19412,250,065 Koehl July 2, 1941 2,485,751 Larsen Oct. 25, 1949 2,505,182Haller et a1. a Apr. 25, 1950 2,506,723 Larsen May 9, 1950 2,598,132Pattyn May 27, 1952 OTHER REFERENCES Publication: The Science of MusicalSounds, by Miller, pp. 192 through 198; copyright 1916, MacMillan Co.,New York.

